Automotive fuel system designers have used a variety of structures for preventing the backflow of fuel from fuel tank filler pipes. These devices are generally held closed by a spring, a counterweight, or, in the case of a duckbill device, the inherent stiffness of the material from which the device is constructed. Unfortunately, each of these devices introduce a restriction into the path of fuel moving through the filler pipe. And, such devices are costly and may be subject to functional problems such as sticking. There has been a marked need, therefore, for a simple, rugged device for preventing backflow of fuel through fuel tank filler pipes, while at the same time allowing higher fuel fill rates.
U.S. Pat. No. 4,760,933 discloses a duckbill type check valve for controlling backflow from the filling orifice of a fuel tank. The duckbill functions as a resilient valve which is normally closed, but which opens when pressure is created in the filler pipe by a column of fuel as well as by the insertion of a fuel nozzle. It has been found, however, that duckbills having sufficient rigidity to prevent backflow have the undesirable trait described above of limiting the flow of fluid into the tank such that rapid filling is not possible. A check valve according to the present invention obviates this problem of restricted flow capacity.
It is an object and advantage of the present invention to provide a backflow preventing check valve which is normally open so that flow capacity in the filling direction is not restricted.
It is another object and advantage of the present invention to provide a check valve which closes at very low reverse flow rates.
It is an advantage of the present invention that fuel may easily be introduced into the tank below the liquid level. This minimizes the aeration of fuel within the tank, thereby minimizing the quantity of fuel vapor generated during filling.
According to the present invention, a fuel tank and filler system for an internal combustion engine includes a fuel tank, a filler pipe extending into the fuel tank, and a check valve comprising a collapsible, normally open tube secured around the outlet of the fuel filler pipe within the tank, such that fuel entering the tank will pass through the filler pipe and then through the collapsible tube, with the collapsible tube having sufficient flexibility to collapse upon itself in the event that fuel begins to flow outwardly through the filler pipe. Fuel is thus prevented from leaving the tank through the filler pipe.